It is proposed to continue developing an efficient route to AT-125 and related derivatives. The next portion of this project will deal with improving the isomer ratio of products derived from the crucial cycloaddition reaction. Steric and associative interactions as outlined in the original proposal will be employed to meet this goal. The sulfone functionality present after cycloaddition will then be transformed to chlorine in two steps as previously outlined. AT-125 itself will then be acheived by deprotection of the carboxyl and amino functionalities. It is also hoped that derivatives where chlorine has been replaced by -NO2 and -F can be obtained from this route.